The present invention pertains to spray drying processes, and more particularly to spray drying processes in which the major vitamin component in the resulting dry product is riboflavin. Prior to the present invention, spray-dried riboflavin processes and products have all involved relatively high amounts of binder (together with other components) therein, i.e., the amount of binder, etc. present approximated the amount of vitamin present. Although a 50% riboflavin product has been found acceptable for use in animal feed formulations, it is desirable to have a much higher vitamin content (i.e., even greater than 90 weight percent vitamin) for pharmaceutical and food applications. The process of the present invention enables the manufacturing of such a product while at the same time, unexpectedly enabling the production of a product having very desirable properties such as high flow rate and low dustiness and low electrostatic clumping and bridging.
Riboflavin is available as a fine powder of various purities (90-100%). This powder is clingy, dusty and highly electrostatic. This powder sticks to and fouls any process equipment with which it comes into contact. Furthermore the powder tends to bridge and clump during handling. There can be significant losses due to a buildup of the riboflavin particles on the processing equipment utilized in food, feed, and pharmaceutical industries. In addition, substantial labor must be expended to remove the adhering material from the equipment.
Prior to this invention, in the pharmaceutical and food industries, ungranulated high concentration riboflavin powders (90-100 weight percent riboflavin) have been used in powder form. However, as noted above, this powder presents flowability, handling, and processing problems. The method of the present invention enables the production of a 90-100 weight percent granulated riboflavin product which has heretofore unachieved flowability characteristics. Furthermore, the process of the present invention enables the production of such a product through the highly desirable and efficient method of spray drying.
The closest related art known to the inventors consists of the following U.S. Pat. Nos.: 4,868,180, 3,962,384, 4,486,435, and European patent application 0,219,276. Although this art is the closest art of which the inventors are aware, none of this art describes spray drying processes for making a high vitamin content (i.e., at least 75 weight percent riboflavin)/low binder product (i.e., below 25 weight percent of binder in the spray dried particulates). Furthermore, none of this art describes any process for producing granule particle sizes with a geometric mean of from about 50 to about 300 microns and wherein the standard deviation of the particle sizes is from about 0 to about 3. In other words, the process of the present invention is the first process for making a spray-dried, granulated riboflavin product having a high riboflavin content. Furthermore, in addition to the high riboflavin content, the process results in the production of spray-dried particulates which have a relatively large particle size. Achieving the large particle size in combination with the high riboflavin content has proven to be difficult. Difficulties were encountered in that in order to make this relatively large particle size, it was necessary to utilize proportionally less water in the mixture being fed into the spray dryer chamber. However, the use of less water in the mixture results in a mixture having a substantially increased viscosity. This mixture cannot be sprayed unless the viscosity is reduced. However, the inventors of the present invention have unexpectedly found that if the mixture is thoroughly homogenized (rather than merely mixed), the viscosity will be reduced to a level at which the "homogenizate" (i.e., homogenized mixture which is homogeneous) is spray-dryable while containing only a relatively small concentration of water, which in turn permits the production of large particle size, high riboflavin content spray-dried granules.
The '384 and '435 patents are directed at compositions which have a binder present in an amount of around 50 weight percent. The use of large amounts of binder (i.e., amounts greater than 25 weight percent, based on total dry product weight) enables the substantially complete granulation of the riboflavin, whereas substantially complete granulation (i.e., less than 10 weight percent ungranulated riboflavin) is much more difficult to achieve if less than 25 weight percent binder is utilized.
U.S. Pat. No. 4,868,180 describes a 90-99% vitamin B granulate which is made by conventional fluid bed granulation, followed by pulverizing the resulting granulate in a Fitz mill. The '180 patent nowhere refers to spray drying. The '180 patent nowhere refers to product yield, (i.e., amount of material lost or adhering to equipment surfaces) completeness of granulation (i.e., level of fines). In contrast to the '180 patent, the process of the present invention is related solely to a spray drying process, as opposed to the fluid bed process described in the '180 patent.
European application 0,219,276 is an equivalent of the '180 patent, discussed above.